3D Underground Cable Localization via Fiber Optic Sensing

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current methods for determining the geographical location and depth of underground optical fiber cables are inefficient, often relying on outdated or incomplete information, and struggle with high-precision localization due to noise interference in vibration-based and electromagnetic wave techniques, especially for smaller objects like fiber optic cables buried in complex soil environments.

Innovation Solution

The use of distributed fiber optic sensing systems, which involve a geophone array and vibration sources to measure the speed of vibration propagation in soil, allowing for the calculation of time of flight and subsequent determination of 3D locations of underground fiber cables by analyzing the time of flight between vibration sources and the fiber, enabling precise localization and depth determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If vibration-based or electromagnetic wave techniques are used for localization, then the ability to detect underground cables is improved, but measurement precision deteriorates due to noise interference from complex soil environments

Engineering Contradiction:

Improvedetection capabilityVSAvoidlocalization precision

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The patent replaces traditional vibration-based mechanical detection systems with an optical-based DFOS system. Optical pulses are transmitted through the fiber cable, and backscattered light is analyzed to detect vibrations caused by excavation equipment. This substitution eliminates the noise interference problems affecting mechanical vibration sensors in complex soil environments, achieving high-precision localization without the measurement precision deterioration that plagues vibration-based techniques.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If traditional excavation methods are used to locate underground cables, then the cables can be found, but the risk of damaging other structures increases and extensive excavation is required

Engineering Contradiction:

Improvecable location accuracyVSAvoiddamage risk to structures

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent performs preliminary localization and depth determination of underground cables using DFOS technology before any excavation activities begin. By precisely identifying the cable's 3D location and depth in advance, the system enables targeted, minimal excavation only at the necessary locations. This preliminary action eliminates the need for extensive trial-and-error excavation, thereby reducing the risk of accidentally damaging other underground structures while ensuring reliable cable location.

Inventive Principle:

Principle #10Preliminary action

3Productivity

If outdated or incomplete information is used for cable localization, then the process is simpler, but localization efficiency and accuracy deteriorate

Engineering Contradiction:

Improvelocalization efficiencyVSAvoidinformation completeness

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The patent employs the fiber optic cable itself as the sensing element, allowing it to self-report its location and detect external vibrations along its length. The DFOS system continuously monitors the cable's position and surrounding environment without requiring external sensors or incomplete historical data. This self-service approach provides complete, real-time information about cable location and depth, dramatically improving localization efficiency and accuracy compared to methods relying on outdated or incomplete construction records.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method provides high-precision, non-destructive localization and depth determination of underground fiber optic cables, reducing the need for extensive excavation and minimizing the risk of damaging other structures, while being more cost-effective and easier to operate than existing techniques.

Implementation Method 1

a time of flight (TOF) between vibration source(s) and underground fiber is used to determine distance therebetween via DFOS

Methodology Applied

Scientific EffectTime of flight: Time of Flight

Implementation Method 2

determine a speed at which mechanical vibrations propagate in underground soil by using geophone array and vibration source

Methodology Applied

Scientific EffectVibration propagation: Vibration

Data Source

PatentUS11681042B2Sparse excitation method for 3-dimensional underground cable localization by fiber optic sensing

Publication Date: 2023.06.20 NEC CORP

AI summary

Aspects of the present disclosure describe distributed fiber optic sensing systems, methods, and structures that advantageously are employed to determine the location and depth of underground fiber-optic facilities that may be carrying telecommunications traffic.